That's anything but a standard PSU form factor. Contact Dell either way, but if you want to continue to use that case ask about a replacement. Otherwise, ask if you can buy a new case/PSU and transfer stuff over. Read something that they have a 10pin CPU connector. You won't have an I/O shield for the back panel and might need a little custom modding to get the dell mobo to fit.
Any chance you have the budget for a mostly new rig? I really don't think throwing money into a P4 DC is a great idea.
I have the first revision and connectors are all different. The computer place that I took it to ordered one, refurbished from Dell but they said it was wrong revision and would not work so I brought it home and thought I would attempt to locat one myself. Where would I find the part number on it? I see a lot of numbers on a tag but no part # stands out.